Thanks GL & Shawn,
There is such an amazing wealth of information in this forum, and there is so very much I need to learn, that in an attempt to not re-ask every single question everyone else who's ever purchased a sailboat askes, I've started reading (from oldest to newest) all of the posts in each section.
Had I read only a dozen more posts in the DSII section, I would found this answer from 2007, which very closes jives with GL & Shawn's responses. It does also give a practical "hands on" solution for lateral adjustments which I will try next time the boat is in an area high enough that the mast can go up again (spring I think). Saves the "trying to level the boat" challenge.
Roger wrote:You don't likely want to invest in a Loos guage at $90 to tension such a small rig, and you don't have to. Once the mast is up, ensure that it is STRAIGHT up. Do this by using a tape measure from the main halyard (taped to the shackle and run up to the top of the mast, then measured to each aft corner of the boat. The measurements should be the same. Adust each shroud by hand to get it equal on both sides, then tighten them by hand. The fore and aft set of the mast should also be 90 degrees from the cuddy sole. If you want mast rake don't have anything further aft than 2 degrees to start with. Tension the forestay to take out any slack using a tool for the last few turns. This will give initial tension to the rig. Now go sailing and notice if there is any slack in the leeward shroud. If there is, tighten them up a few turns (each side equally) with a tool. When you are sailing on a beam reach, the leeward shroud should be 'just' slack, not sloppy. Continue to adjust each shroud equally until you get this tension. Now to focus on the mast rake. Your boat should ideally round up into the wind and stall within a few boat turns when you let go the tiller. This is called weather helm. If you are fighting the tiller all the time, then you have too much weather helm. If your boat turns downwind, you have too much lee helm. To increase weather helm, reduce tension in the forestay and increase the tension in both shrouds so that each shroud still has equal tension. This will move your mast back and thereby the center of effort, which will increase weather helm. If your boat is perfectly balanced (bad) or turns downwind, (even badder), then slack off (equally the tension in the shrouds and increase the tension in the forestay. Only do a few turns at a time. It may take you several sails to get the boat where you can control the tiller with finger tip control, yet still have it round up into the wind if you let go the tiller. Once you have that, lock your turnbuckles with wire, mark them, or tighten down the restraining nuts so that they do not change over time. If using shroud adjusters, mark the holes. Shroud adjusters will not allow as fine tuning as turnbuckles.
Shrouds will stretch over time, and new ones will stretch in the first few seasons, so will need readjustment in the first few years.
If you do have a Loos guage, follow the directions for setting tension, but you still have to go through the above procedure to get the mast straight from side to side, and the rake perfect to get some weather helm. All that a Loos guage does is identify the amount of tension based on the size of the shroud.
I've also printed out the linked North Sails instructions and will stuff them in my sail bag as a reference for next year.